Investigation of high-dose chemotherapy (HD-CT) compared with standard-dose chemotherapy (SD-CT) as adjuvant treatment in patients with primary breast cancer and >/=10 axillary lymph nodes. From November 1993 to September 2000, 307 patients were randomized to receive after four cycles of epirubicin (90 mg/m(2)), cyclophosphamide (600 mg/m(2)) i.v. (every 21 days) and either HD-CT of cyclophosphamide (1500 mg/m(2)), thiotepa (150 mg/m(2)) and mitoxantrone (10 mg/m(2)) i.v. for four consecutive days followed by stem cell transplantation or a SD-CT of three cycles CMF (cyclophosphamide 500 mg/m(2), methotrexate 40 mg/m(2), 5-fluorouracil 600 mg/m(2), i.v. on day 1 and 8, respectively, every 28 days). After a median follow-up of 6.1 years, 166 events with respect to event-free survival (EFS) (SD-CT: 91, HD-CT: 75) have been observed. The hazard ratio of HD-CT versus SD-CT is estimated as 0.80 [95% confidence interval (0.59, 1.08)], P = 0.15. The trend to a superiority of HD-CT as compared with SD-CT with respect to EFS seems to be more pronounced in premenopausal patients as compared with postmenopausal patients and in patients with tumor grade 3 as compared with patients with tumor grade 1/2. With a follow-up of 6 years, there was a trend in favor of HD-CT with respect to EFS not being significant. A proper meta-analysis needs to be undertaken for an evaluation of subgroups of patients who might benefit from HD-CT.